Chapter 8: Comparing Fingerprints

The old desktop computer whirred and creaked as it operated.

A whoosh of warm air blew out from the case, dissipating into the room.

In a moment, the right side of the LCD screen displayed the top 20 fingerprints with the highest match value.

Jiang Yuan wasn't in a hurry. He took a sip of tea and then clicked to examine the first fingerprint.

These past few days, due to the murder case of Uncle Seventeen, the entire criminal police force had been running at full capacity. Suddenly things had eased, and Jiang Yuan had returned to the routine of a forensic doctor—appearing to have little work to do.

Meanwhile, he was gradually getting proficient with the newly-acquired system reward, "Chongqing Single Finger Fingerprint Analysis Method—Bow Pattern Identification (lv3)" through practice.

After some exercises with his study workbook and public materials, Jiang Yuan decided to put his skills into practice: first, to identify a bow-patterned fingerprint, and then determine to whom it belonged.

For the first step, he chose a fingerprint collected from a robbery case in the neighboring city of Longli County.

The reason he didn't choose a fingerprint from a murder case was the "all murders must be solved" principle, which means these cases are given great importance, especially before becoming cold cases, with fingerprints undergoing thorough comparisons. The fingerprints from murder cases that remain in the database are bound to be extremely challenging.

If Longli County had an unsolved murder case with a suspected perpetrator's fingerprint lifted, that print would first be compared multiple times by the local trace examiners. If it didn't match, efforts would be made to lift additional prints on-site. If all attempts failed, the municipal Criminal Science and Technology Squadron would be called in for assistance, or even directly approaching the provincial department was possible.

If the print remained unmatched at the provincial department level, with the case still unsolved, then every year or two, the department and ministry would organize special fingerprint comparisons for major cold cases. Participants would often be forensic experts from the criminal technology talent pools of the provincial department or the ministry's youth talent pool.

Jiang Yuan had already experienced the LV3 egg fried rice, so his expectations for the LV3 bow-patterned fingerprint identification weren't that high.

The egg fried rice tasted great, but it didn't glow.

By that logic, LV3 bow-patterned fingerprint identification must be impressive, but not godlike.

Moreover, the fingerprint databases he had access to were limited. Starting with a murder case as the first fingerprint to analyze, Jiang Yuan thought, would be too easy for a setback.

In contrast, a robbery case seemed more suitable for the time being.

On one hand, ordinary robbery cases wouldn't reach the provincial department's level of major cases. On the other hand, the seriousness with which robbery cases were handled at the county bureau level determined the initial forensic officers would be serious enough when lifting fingerprints. The fingerprints uploaded to the database were surely highly relevant to the case.

That said, Jiang Yuan was quite surprised when he first opened the fingerprint image for this case.

The print was lifted under unknown conditions, not only blurty but also incomplete, amounting to only about half of a normal fingerprint. Fortunately, more of the fingertip area was preserved, providing a basis for comparison.

Beyond that, distortion of the fingerprint was not even worth mentioning.

This was vastly different from the fingerprints left by ordinary people when clocking in for work. Without some level of professional expertise, it's not just about marking characteristic points, even determining which finger it was could be difficult.

As expected, none of the 20 automatically matched fingerprints by the system matched.

Jiang Yuan wasn't discouraged. Such fingerprints were uploaded to the system precisely because the local trace evidence examiners had trouble matching them. The reason for the local failure could be technical issues or perhaps the database simply didn't contain the corresponding fingerprints.

If it was the latter, there was nothing Jiang Yuan could do but hope that the scope of the bureau's fingerprint database was larger... And that's what he was banking on with the former.

For the forensic officers making fingerprint matches, effort was essential; only by putting in the effort was there a chance to rely on luck.

Jiang Yuan closed the fingerprint comparison page and re-opened the suspect's fingerprint image, this time using Photoshop.

He observed the state of the incomplete fingerprint carefully and then started to adjust the contrast and brightness.

Jiang Yuan's adjustments were so meticulous that even a slight enhancement in the clarity of the fingerprint image took half an hour.

However, sharpening the ax wouldn't delay the work of chopping wood. Once Jian Yuan had everything ready, he took a closer look at the fingerprint image, and the direction of the lines became much clearer.

He then made a slight adjustment to the center of the fingerprint.

The center point was uncertain due to the severity of the fingerprint's incompleteness. If Jiang Yuan didn't adjust it, the system would automatically estimate a center point.

Watching the patterns' flow, Jiang Yuan redefined the center point and then returned it to the software, adjusted the settings, and hit confirm once more.

Another 20 fingerprints, none of which matched.

He adjusted the center point again and compared once more...

This time, Jiang Yuan immediately noticed the third fingerprint on the list.

To ordinary people, at a glance, fingerprints might all seem similar, especially those classified as bow-patterned or tented arches—it can often be very difficult to distinguish.

But for someone who has been looking at fingerprints continuously, different fingerprint characteristics become as familiar as freckles on an old sow's face after a while.

Jiang Yuan directly opened the third fingerprint, enlarged it, and placed it on the right side of the computer screen, then opened the original fingerprint and placed it on the left side.

When the two fingerprints were placed side by side, their similarities became unmistakably evident.

At this point, it was no longer just about looking at characteristic points but rather about judging the degree of similarity between the fingerprints. When it comes down to one-on-one, the human eye's ability to differentiate is much stronger than a computer's.

"Got a match!" Jiang Yuan muttered to himself, feeling a wave of relief as he casually submitted the matching fingerprint.

According to the rules, his submitted print would go to the provincial department experts for review. Once they confirmed it was accurate, they would click submit, and someone would notify the corresponding front-line unit to arrange for the arrest.

Of course, it's no problem for the local criminal police to make an arrest if they want to do so.

That was beyond Jiang Yuan's concern; he stretched languorously, got up to stretch his muscles, and checked the time, contentedly waiting for the end of his workday.

Life as a forensic doctor without bodies was simple and pure.